This invention relates generally to tubular linings for pipelines or passageways which linings are of a type known as `softlinings` or `cured in place` linings which employ resin absorbent material which is impregnated with curable resin which has been conditioned in order that it may be cured to produce a pipe on the surface of the pipeline or passageway (typically an underground sewer) thereby in effect forming a pipe within a pipe.
The lining to which the invention relates is a resin absorbent tubular structure (herein the "lining tube or pipe") which is to be used for lining an underground pipeline or passageway such as a sewer. In such utilization, which is now practiced widely throughout the world, the impregnated lining tube is inflated (by gas such as air, steam and/or liquid such as water) against the pipeline or passway surface whilst the resin is uncured, and whilst the lining tube is so held in position, the resin is allowed or caused to cure whereby the cured resin with the absorbent tubular structure embedded therein forms a self supporting rigid pipe, which may or may not bond to the pipeline or passageway wall. The purpose of this operation is to rehabilitate and/or repair the passageway or pipeline. A particular advantage of the provision of a self supporting rigid pipe is that bonding to the existing pipeline is not necessary, as is the case with some lining systems but it is to be mentioned that this invention can be applied to pipelining systems where the impregnated tube does bond to the existing pipeline or passageway, such systems being those wherein the lining tube is of relatively small thickness e.g. 5 mm or less and the resin acts like a bonding medium rather than an impregnating medium.
Also the lining tube when the resin is in the uncured state may not strictly be a tube in that it may be a web folded into tubular form so that its edges overlap and such edges become fused or held relatively together only when curing in place has been effected. In fact, this arrangement provides the advantage that the overlapping edges can slip relatively as the tube is being inflated so that the tube will best fit to the passageway surface.
Examples of methods of lining of underground pipelines and passageways using impregnated lining tubes which are cured in place are contained in many patent specifications of which examples are U.K. Patent No. 1,340,068, which is the original patent for this technology, and U.K. Patent No. 1,449,445.
All or by far the majority of the methods which are practised throughout the world using cured in place lining tubes for lining underground pipelines and passageways simply use a heat curable resin (e.g. polyester and heat for the curing of the resin, the application of heat causing a catalyst and/or promoter (accelerator) in the resin to release free radicals and commence cross linking of the resin molecules and crystal formation; the curing reaction is exothermic and heat is internally generated and the curing process accelerates.
One disadvantage of this arrangement is that even if heat is not applied to the impregnated lining tube, under ambient conditions the resin will eventually cure in a matter of days and of course if curing takes place before the lining tube is in place on the passageway of pipeline surface, the lining tube is completely lost and must be scrapped. This can represent a considerable loss if not a complete loss of profit on a contract. Should the lining tube cure when it is part way inside the pipeline or passageway, then the consequences financially could be disastrous for the contractor. In order to avoid the problem of the resin curing too soon, i.e. before the lining tube is in place, contractors have resorted to extensive measures, in particular to keeping the impregnated tube refrigerated until it is to be used on site. This means that the tubes must be delivered to the site in refrigerated vehicles.
The effect of this procedure is that the contractor is limited in terms of when he can mix the resin and impregnate the lining tube.
Ironically, however, once the tubes have been put in place, it is desireable that the resin should be cured as fast as possible, as the sooner the resin cures, the sooner the contractor can leave the site. It is to be noted that the contractor will often be given or will often quote a relatively short time for completion of the work, usually undertaken during the night. It is very important therefore that the work be completed in the shortest possible time, especially in these cases where the performance of the work involves the rendering inoperative (as it does in many cases) of a sewage system or the blocking or obstructing of traffic.
To perform the contract therefore the contractor must on the one hand have a factory or plant at which the tube is impregnated, a vehicle for keeping the impregnated tube refrigerated and a vehicle with a heating means for heating the fluid which inflates the tube when in place, in order to effect the curing of the resin, as well as the necessary equipment for putting the tube into place.
There is also the dilemma concerning the resin. On the one hand it is desireable that it should have as long a shelf life as possible to give the contractor plenty of time to place the tube in the pipeline or passageway before curing. On the other hand, when the tube is in place, it is desireable that curing should take place as quickly as possible. Unfortunately this dilemma has proved so far to be insoluble as the additives such as retarders for the resin which can increase shelf life of the resin also increase the cure time of the resin.
Consequently, when a contractor has to perform a contract, he must have the lining tube manufactured, and, immediately before he is to insert the lining tube, he impregnates the tube with the resin, transports it to site (which may be remotely located) as quickly as possible, and inserts the lining tube and cures it as quickly as possible. As soon as the resin is mixed with its catalyst for impregnation of the lining tube, there is a time countdown, and the contractor is racing against time.
The industry is aware of this problem and some attempts have been made to solve it by developing special resins which are `quiescent` or `latent` and do not cure for a long time until activated by some external source which are examples of resins curable by light radiation, such as are disclosed in European Patent Specification No 0007086, and methods of cured in place lining with impregnated lining tubes using light radiation are disclosed in U.S. Pat. No. 4,581,247 and 4,680,066.
Light radiation curable resins however include catalysts which are activatable by the suns rays and therefore the impregnated lining tubes must be contained in opaque wrappings during storage and transportation to avoid premature curing.
Light radiation curable resin does however have the advantage that curing of same can be controlled and theoretically the resin has an infinite shelf life. When it comes to curing the in place impregnated tube however, problems arise. Thus, special ultra violet light sources are needed to cure the resin; and when, as is often the case, the inflating medium is water, that water may be dirty in which case light curing cannot be performed. When the flowing liquid in the pipeline or passageway is opaque, as sewage is, it must be diverted and the use of light curing equipment suffers from the same disadvantage in this respect as heating-methods. For these reasons, in practice, light curing of in place impregnated lining tubes has not been successful and has not replaced the traditional heating methods.
The invention the subject of International Patent Application No. PCT/GB93/00107, of which I am joint inventor, seeks to provide latent curable resin systems for the production of rigid articles wherein the resin can be cured readily and quickly, but retains a long to infinite shelf life (e.g. one year or more) making it particularly suitable for use in cured in place lining systems for pipelines and passageways.
According to the invention the subject of said International Application in its most general aspect the resin includes or is located adjacent inert matter which is not affected by ambient conditions such as ambient heat and light, but such matter is susceptible to applied radiation to such an extent to cause curing or commencement of curing of the resin.
There are various forms which the said matter can take, and such forms can be used singly or in combination.
In one specific example, the matter comprises microencapsulation shells in which is contained a catalyst for the resin, or a promoter (accelerator) or both, the shells being susceptible to the ultrasonic radiation to rupture the cells to release the catalyst/promoter, and hence cause commencement of the cure.
Difficulties with the use of means capable containing catalysts/accelerators have been encountered. Thus, it is difficult to produce the micro-capsules. Secondly, it is difficult to produce micro-capsules of sufficiently small size so that they will satisfactorily be spread throughout the absorbent material of the lining. Thirdly, it is not easy always to rupture the micro-capsules to release the resin and if rupture is not even and homogenous, cure can be uneven, which is highly undersirable.
The said International application also describes the use of individually heatable particles (iron particles) in the resin, but the difficulty with this concept is that it requires the use of an electrical induction source of high frequency inside the pipeline which may be full of water, and the problems associated therewith have not been solved.
The present invention has as its object to provide a lining tube impregnated with a latent resin system which can be selectively activated for the cure of same more predictably and normally quicker than the known proposals.
According to the present invention there is provided a lining tube comprising an absorbent layer impregnated with a resin system which comprises a resin matrix and a catalyst and/or an accelerator, characterised in that the catalyst and/or accelerator is absorbent in micro pores of microporous particles distributed throughout the resin matrix.
By having the catalyst and/or the accelerator absorbed in the micropores of the particles, as opposed to contained in shells of microcapsules, considerable advantages are obtained including that the catalyst and/or accelerator can be released into the resin matrix much lesser than in the case of replacing the microshells. For example, the application of heat has been found to cause opening of the pores of the microporous particles and quick release of the contained substance which leads to rapid and even cure of the resin matrix, which is important in the application of lining underground sewers.
The release of the contained substance can also be achieved by the application of ultrasonic energy, which achieves opening of the said pores by the mechanical and heat energy generated in the resin matrix, and ultrasonic energy can readily be passed through liquid especially water and there is no difficulty in using such energy inside an underground pipe.
Again, it is possible to include in the resin matrix cure enhancing particles of a material which is susceptable to the electromagnetic variation of an alternating magnetic field and will heat up due to eddy current and hysteresis losses. The heat guaranteed by such particles can be used for the opening of the pores of the absorbent particles.
Microporous particles as used in the invention will have a maximum size having agreed to the fact that they must be dispersed throughout a resin absorbent material, such as a fabric, typically a needled felt and in this connection the particles would be unlikely to exceed 100.mu. in size. They would more likely be in the range up to maximum of 15.mu. to 20.mu. and optimally we would prefer that the particles be in the size range 7.mu. to 15.mu.. It is appreciated that in any mass of particles, there will be a particle size distribution and some particles will be of a size above the range whilst others will be of a size below the range.
The micro porous particles may comprise clay particles and the clay particles may be arranged in two groups, one of which has a catalyst adsorbed therein, whilst the other group has the promoter adsorbed therein. When the resin matrix is a polyester resin the catalyst preferably is Dibenzoyl Peroxide, and the promoter is an amine. In such case, the clay of said one group preferably is different from the clay of the other group.
Clay particles are made up of micro platelets having micro pores therebetween which form the pores into which the catalyst and/or promoter is absorbed. In tests carried out it has been found that on using clay particles supplied by In Porte under the description FULMONT XMP4 of particle size normally 20.mu. the clay particles absorbed the catalyst Benzoyl Peroxide to an extent that up to 60% of the final particle weight comprised the Benzoyl Peroxide. Also clay particles supplied by In Porte under designation CP639 of nominal particle size 15.mu. absorbed the amino accelerator diethyl aniline to an extent to form 30% of the weight of the final particle.
Using these "filled" microforms particles in a resin matrix of polyester Crystic 397 supplied by Scott Bader and subjecting it to ultrasonic energy as explained in more detail herein provided an effective resin cure.
The catalyst and the promotor were absorbed into the clays by the use of ultra sonic energy. It is believed that this energy drives the molecules of the catalyst and the accelerator into the micropores of the particles and to achieve this the catalyst and accelerator should have a molecular size (as indicated by molecular weight) to enable this to take place. The molecular weight of each of Benzoyl Peroxide and diethyl aniline as approx 100.mu. and is sufficiently small so that the molecules thereof can be driven into the fores of the particles.
The concept of driving catalyst and/or accelerator into the pores of the microporous particles is an important ancillary feature of the invention and also is an independent invention.
The Polyester resin matrix on the other hand has a molecular weight in the order of 10,000 and therefore when the mixture of resin matrix and microporous particles is subsequently subjected to ultrasonic energy the resin molecules will not enter the pores but will bombard the microporous particles, releasing the absorbent catalyst and/or accelerator providing a rapid and even cure.
The particles of clay it should be mentioned are held together to form the particles by electrostatic action, and the aforesaid bombardment also generates heat. Heat has a thermo electric effect which destroys the electrostatic attraction between the platelets so that the pores open and this enhances the effect of release of the catalyst and/or accelerator so that curing takes place evenly and rapidly.
Instead of applying ultrasonic energy to release the catalyst and/or accelerator, heat may be applied by other means to produce the same effect. Thus, heat may be applied in the conventional way using hot water, hot gas or steam.
Another method involves embodying in the resin along with the microporous particles additional particles which can be heated by applied radiation, such as ferromagnetic particles, especially ferrite particles having a CURIE temperature. When such particles are heated by such radiation, the heat in the additional particles provides the same effect as described above for the release of the catalyst and/or accelerator and rapid and even core of resin matrix.
In a modification the said additional particles may form the impervious particles, if they are of the appropriate structures having pores for the absorbing of the catalyst and/or accelerator. In such case, the inductive heating of the particles should provide even further release of the catalyst and/or accelerator, and more rapid cure of the resin matrix.
To enhance the release of the catalyst and promoter when the resin and microporous particles are subjected to the energy to release the catalyst and promoter, the resin may include the additive hexametaphosphate which functions to release the catalyst and promoter at an accelerated rate.
When an ultrasonic generator is used to release the catalyst and/or promoter, the ultrasonic generator described in International Patent Application No PCT/GB93/00107 or in U.S. Pat. No. 5,200,666 may be used.
As stated herein it has been found that the use of ultrasonic energy can achieve impregnation of various materials into others and as applied to the lining of underground pipelines and passageways as discussed above, a curing agent can be caused to be absorbed into the pores of micro porous particles and also that the particles themselves can be caused to be absorbed in an absorbent lining material.
According to the present invention therefore in another aspect, a first material is caused to impregnate a second material by the application of sonic energy to the materials when in close proximity.
In one example, where a resin curing agent in liquid form is mixed with microporous particles, and sonic energy is applied thereto it has been found that the curing agent is absorbed into the particles. The amount of curing agent which is taken up by the particles depends upon the level of and length of time of application of the sonic energy but good results have been obtained using Benzoyl Peroxide as the curing agent and Bentonite of average particle size of 5 micron.
It has also been discovered that the particles, such as the microporous particles mentioned above, with or without the Benzoyl Peroxide adsorbed therein, can be caused to impregnate textile sheets such as the felt sheets used to provide the absorbent materials of underground pipe linings, by the application of sonic energy. Thus, if the particles are carried in a liquid in suspension, and a piece of the felt is immersed in the suspension and an ultrasonic probe is inserted therein and driven, the particles are observed to move into the spaces between fibers of the felt, thereby to impregnate the felt which, as explained hereinafter is of considerable advantage in the field of lining pipelines and passageways in which we are particularly interested.
In order to illustrate the various aspects of the invention reference will now be made, by way of example, with reference to the accompanying diagrammatic drawings, wherein:
FIG. 1A is an enlarged view of a typical microporous clay particle;
FIG. 1B is a view of the particle of FIG. 3A when it contains a resin curing agent (catalyst or accelerator);
FIG. 1C is a view of the particles of FIG. 3A as it releases its curing agent;
FIG. 2 is a graph showing the release of curing agent from the particles under various conditions;
FIG. 3 is a graph showing the release of curing agent under various conditions and when the a resin is modified;
FIG. 4 is a sectional side elevation showing a lining operation in progress, the operation being for the application of a flexible lining tube according to the invention to an underground passage;
FIG. 5 is an enlarged sectional elevation of the lining tube which is adopted for the process of FIG. 1; and
FIG. 6 is a perspective view illustrating how the lining tube is everted into position in the pipeline or passageway.